Self-Heating in GaN Transistors Designed for High-Power Operation

• Published in: IEEE transactions on electron devices 2014-10, Vol.61 (10), p.3429-3434
• Main Authors: Kuzmik, Jan, Tapajna, Milan, Valik, Lukas, Molnar, Marian, Donoval, Daniel, Fleury, Clement, Pogany, Dionyz, Strasser, Gottfried, Hilt, Oliver, Brunner, Frank, Wurfl, Joachim
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitride; Aluminum gallium nitrides; Buffers; Devices; Gallium nitride; Gallium nitrides; GaN; HEMTs; high-electron mobility transistor (HEMT); Implantation; Optical buffering; optical characterization; Semiconductor devices; Silicon carbide; Substrates; thermal characterization; thermal resistance; Transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2014.2350516

DC and transient self-heating effects are investigated in normally off AlGaN/GaN transistors designed for a high-power operation. Electrical and optical methods are combined with thermal simulations; 2-μs-long voltage pulses dissipating about 4.5 W/mm are applied on four different transistor structures combining GaN or AlGaN buffer on an n-type SiC substrate with or without Ar implantation. Transistors with only 5% Al mass fraction in the buffer show almost a threefold increase in the transient self-heating if compared with devices on the GaN buffer. On the other hand, 2-μs-long pulses were found not to be long enough for the Ar-implanted SiC substrate to influence the device self-heating unless AlGaN composition changes. In the dc mode, however, both the buffer composition and Ar implantation significantly influence the self-heating effect with the highest temperature rise for the transistor having the AlGaN buffer grown on the Ar-implanted SiC. We point on possible tradeoffs between the transistor high-power design and the device thermal resistance.